Airflow (V), tidal volume (TV), and EEG polygraphic recordings were performed in 30 normal full-term newborns (FTN) and in 10 premature newborns (PN). Besides the classical expiratory flow (CEF), a retarded expiratory flow (REF) was observed: a phase of slow flow ending with a sharp increase. REF was mostly encountered in quiet sleep (QS) in FTN. During REF, Te and Ttot became longer; Ti became shorter, with an increase in TV. In QS, sighs were more numerous in FTN with a high percentage of REF. Expiratory sudden short arrests of airflow (SSAA), less than or equal to 2 s, during expiration were more frequent in active sleep (AS) in FTN. REF may be due to some obstruction or to postinspiratory diaphragmatic activity; variations in functional capacity may also be involved.